Apparatus and method for producing very high velocities



APPARATUS AND METHOD FOR PRODUCING VERY HIGH VELOGITIES 5 Sheets-Sheet 1 Filed Aug. 20, 1962 INVENTOR-S (flaw/es J. God/reg. BY Frank/m C. Fara.

p 1965 c. s. GODFREY ETAL 3,204,527

APPARATUS AND METHOD FOR PRODUCING VERY HIGH VELOGITIES 5 Sheets-Sheet 2 Filed Aug. 20, 1962 ofl m T 0 N w w 5m k A rn Mm 6F Y B ATTOEK/KYJ- APPARATUS AND METHOD FOR PRODUCING VERY HIGH VELOCITIES Filed Aug. 20, 1962 5 Sheets-Sheet 3 Bad/a; cm

0 4 6 /2 /6 Z0 Z4 Z6 32 36 4 0 44 48 52' 77/21 a /7/c/'0 -Jecon ds jgi 0 4 6 /2 /6 Z0 Z4 Z8 .32 36 40 44 46 .52 J6 O 77/776 Mmro-feconas INVENTORS Fi 5 fiar/es & Gad/reg.

BY Frank/m 63 Ford United States Patent 3,204,527 APPARATUS AND METHOD FOR PRODUCING VERY HIGH VELOCITIES Charles S. Godfrey, Berkeley, and Franklin C. Ford, Pleasanton, Calif, assignors, by mesne assignments, to Physics international Company, Berkeley, Calif., a corporation of California Filed Aug. 20, 1962, Ser. No. 218,008 18 Claims. (Cl. 89-8) The present invention relates, in general, to the acceleration of projectile bodies to very high velocities and, more particularly, to methods and apparatus systems for accelerating such bodies to hyper-velocities greatly in excess of those produced by commonly known systems.

With the advent of the space age a pressing need has arisen for a feasible means of accelerating or otherwise propelling small size projectiles or other solid particulate matter, as well as gaseous bodies, at velocities considerably in excess of those generally attainable using classical or conventional systems. For example, micro-meteorites traverse inter-stellar space at very high velocities and in sufficient numbers to present a serious hazard to missiles,

satellites and other space vehicles. In the absence of a feasible means for producing similar projectiles, terrestrially, the study of the effects of such projectiles upon vehicle surfaces and other vital components cannot easily be effected.

The testing of structures designed to minimize damage from such impinging solid projectiles or gaseous bodies must be performed in a manner simulating actual space conditions.

Micro-meteorites are particles of varying composition being generally of less than about a gram in mass ranging downwardly to cosmic dust of micron or sub-micron dimensions. These particles travel at velocities of the order of several centimeters per microsecond or above. (1 cm./-microse-con-d=3.6 kilometers/hour.) Due to the high velocity thereof, a micro-meteorite comprises an intensely concentrated packet of kinetic energy. Therefore, upon collision with a solid surface categorically different effects are noted as compared to those obtained with lower velocity projectiles. The sudden conversion of the kinetic energy of such particles into shock wave and heat energy produces destructive effects, such as cratering, quite out of proportion to the size of the impinging particle. The controlled impact of high velocity particles on solid surfaces could also be employed in highly advanced equation of state studies as well as in dynamic stress studies. Moreover the chemical conversions and changes of state produced by such collisions should produce new and valuable forms of matter. Bodies moving at the indicated velocities might also be employed in studies of the interaction with selected atmospheres such as to simulate reentry conditions and to determine effects such as ablation and others which are of interest to theaerospace industry. Gaseous jets or other high velocity gaseous bodies may be employed for similar purposes.

It is presently conceived that a practically feasible system for conducting operations of the character described can be constructed utilizing an especially constituted and arranged explosive system to accelerate or propel particulate and other projectile bodies to attain hypervelocities of the magnitude indicated above. Classical explosive systems such as firearms and the like are not capable of attaining velocities which even approach those in lower and intermediate ranges of those contemplated herein, particularly in a form meeting the space limitation of laboratory installations. Inherent characteristics of such classical systems provide insurmountable ob- 3,204,527 Patented Sept. 7, 1965 stacles. Among these inherent characteristics are low energy concentration and excessively low effective gas velocities and pressures of the propellant gases.

However, in accordance with the present invention there is utilized a high explosive material of maximum energy content having a structural configuration especially adapted to compress and heat a selected gaseous propellant material to provide a highly collimated, ultra-high velocity jet of propellant gas. Such jet, wherein a significant proportion of the explosive energy is present in an exceedingly high concentration and Whose composition may be selected to achieve optimum or other desired properties, may be directed to propel a projectile body or gas appropriate for the desired purpose. As a prime additional feature of the invention a modification of the basic explosive device is provided whereby the energy content of the propellant gas is increased by means of an electrical discharge which, cooperating with the explosive energy, provides even higher effective propellant gas velocities.

A distinct advantage of the present system resides in the circumstances that the composition of the propellant gas may be determined with certainty and remains substantially uncontaminated with cavity liner and explosive residues. Moreover, a great variety of projectile bodies may be employed in a variety of ways to provide a great latitude and flexibility with regard to the experiments and studies which can be performed. Projectile bodies may be accelerated with little change in mass or shape wherefore the reproducibility of results and more instructive data can be obtained. Moreover, propellant gas jets produced as described hereinafter comprise an exceedingly bright light source which is believed to exceed by several orders of magnitude any available on earth, other than nuclear blasts, with respect to the radiation intensity emitted per unit of area.

Accordingly it is an object of the present invention to provide methods and means for accelerating and propelling a variety of projectile bodies to very high velocities.

Another object of the invention is to utilize a high explosive appropriately formed to compress and heat a selected gaseous material to provide a collimated very high velocity, high temperature gas jet of predetermined composition.

Still another object of the invention is to utilize a high explosive arranged in such a manner as to compress and heat a selected gaseous material to provide a collimated, hyper-velocity propellant gas jet suitable for propelling solid and other projectile bodies to very high velocities.

One other object of the invention is to provide a hypervelocity system in which there is utilized an assembly including a high explosive, appropriately constructed and arranged to compress and heat a selected gaseous material in such a manner that supplementary energy may be introduced by means of an electrical discharge into said gaseous material providing thereby a collimated jet of very high velocity gas suitable for propelling a variety of projectile bodies.

A further object of the invention is to provide a hypervelocity system wherein there is established a controlled environment and in which there is utilized an explosive charge especially shaped and arranged to compress and heat a selected gaseous propellant material to form a collimated jet and including launching or guiding means whereby a selected projectile body can be accelerated and propelled to very high, i.e., hyper-velocities.

Other objects and features of the invention will be set forth in the following description and accompanying drawing in which:

FIGURE 1 is a diagrammatic cross-sectional view of a controlled environment chamber of a hyper-velocity system in accordance with the invention;

FIGURE 2 is an enlarged cross-sectional view of the projectile launching unit assembly shown in FIGURE 1 including additional details;

FIGURE 3 is a cross-sectional view of the projectile launching assembly of FIGURES 1 and 2 shown in progressive stages of a typical operation;

FIGURE 4 is a family of curves plotting inner liner radius versus time for various initial radii;

FIGURE 5 is a set of curves similar to those of FIG- URE 4 but with time displacement based on detonation time at the various initial radii;

FIGURE 6 is a cross-sectional view similar to FIG- URE 2 of a modified projectile launching unit assembly; and

FIGURE 7 is a partial cross-sectional view similar to FIGURE 2 showing another embodiment of the invention.

In brief, the high explosive components of the hyperveloeity system of the invention are provided as a unitary assembly including a shaped high explosive body wherein there is provided a cavity. characteristically such cavity is provided with a liner material which is designed to efficiently utilize the explosive energy imploding thereon to provide a progressive controlled collapse thereof. The lined cavity contains a selected gaseous material which is compressed and heated by the collapsing liner and which is ejected from the cavity as a very high velocity, very high temperature, substantially uncontaminated jet of determined composition. Said assembly includes a detonator and is usually provided with tamper case means as Well as with means appropriate for introducing the gaseous material into said cavity. When augmented output is desired, means are provided for producing a preheating electrical discharge in said cavity. As typically employed, such an assembly is arranged in a controlled environment system together with other components including means for positioning, launching and guiding a projectile body under the impetus provided by the gaseous propellant jet produced by the explosive assembly.

More particularly, as shown in FIGURE 1 of the drawing, a hyper-velocity system in accordance with the invention may be provided within an elongated closed cylindrical vessel 11. As typically employed for accelerating and propelling projectile bodies, a unitary explosive assembly 13 is disposed in one end region of vessel 11 and is supported by a transverse wall or spider element 15. The assembly 13 together with a launch tube or barrel 17 constitute an explosive propulsion or projectile launching unit 16. The tube 17 is directed longitudinally away from assembly 13 so as to be aimed directly at a target or stop 19 supported by a transverse wall 21 in the opposite end region of vessel 11.

Vacuum pump means (not shown) may be coupled to conduit 23 for evacuating vessel 11 and a gas supply (not shown) such as of air, nitrogen, noble gas or the like, may be coupled to conduit 25 for supplying a desired atmosphere at a selected pressure to fit the needs of various experiments. The transverse wall 15 and Wall portions of vessel 11 form a cavity 27 for receiving the explosive assembly 13. The walls of cavity 27 should be of heavy construction and armored as needed to contain explosive gases and fragments. For convenience of assembly a flanged joint 29 may be provided in the circumferential walls of vessel 11 as in the region of the transverse wall 15. Wall 15 itself or a central portion thereof may be made removable if desired to facilitate assembly particularly in repeated operation. A pressure operated valve 31 may be provided to allow explosion gases to escape from cavity 27.

A conduit tube 33 may be employed not only to support the barrel 17 but also for the purpose of introducing a selective gas therein, as will be seen more clearly hereinafter. The muzzle of the barrel 17 may include a thin metal foil or plastic film 34 to prevent escape of gas.

A muzzle blast shield 35 is provided as an armored wall disposed transversely across the vessel 11. The shield 35 is provided with a curved surface flange 39 which defines a central opening 37 coaxially aligned with the barrel 17.

Various types of instrumentation may be employed for observing effects and determining velocities, etc., achieved within the system. For example, thin films or screens 41 may be disposed in insulated rings 43 supported by spider brackets 45 with'the known spacing along the path traversed by the projectile bodies connected in electrical conductive circuits (not shown) to serve as range velocity sensing elements. Disruption of the circuits may be viewed by oscilloscope methods to determine the time of travel between the spaced films wherefrom the velocity may be calculated. In the event that the projectile is magnetic, sensing pickup coils may be substituted for the films. Sensing coils may also be used if the projectile body produces ionization along its path in sufiicient amounts to disrupt a steady magnetic field produced by a D.-C. current flowing in said coils. Spectrascopes, electro optical sensing devices, and flash X-ray devices may be positioned along the path such as at the windows 47.

A complete system may include an electrical detonating pulse generator 49 connected to the explosive assembly 13 for initiating the detonation of the explosive assembly. There may also be included a timing sequence pulse generator 51 coupled to provide a timing pulse to actuate the generators 49. In addition, the pulse generator 51 may be coupled to provide a timing pulse to actuate a power source 53 connected to the explosive assembly 13. As will be seen hereinafter the power supply 53 may be employed for supplementary excitation or pre-excitation of the propelling gas within the explosive assembly.

The explosive assembly 13, as can be seen more clearly in FIGURE 2, preferably includes a quantity of high explosive material 55, an inner liner 57, and outer tamper case 59. The explosive assembly includes two sections, a forward or cavity shaping section 61 and a rearward or detonating section 63. While each of these sections 61 and 63 are shown conical in hape, other configurations may be employed as will be explained hereinafter.

The explosive assembly further includes a detonator '65 connected by a line 67 to the pulse generator 49 (FIGURE 1). The rearward portion 63 of the explosive assembly 13 merely serves as an extension of the detonator 65 whereby the high explosive in the forward section 61 may be ignited. The forward section 61, on the other hand, provides the function of forcing the atmosphere within the explosive assembly, that is, within the chamber 69, outward through the orifice 71 and the barrel 17. Thus, the shape and the composition of the various layers of the forward section 61 must be adjusted to provide that the cavity 69 close in a proper sequence.

The tamper case 59 in both the forward 61 and rearward 63 sections serves to provide an inertial backing for the detonating high explosive 55 such that the force of the explosion is directed toward the center of the assembly 13. This is accomplished by constructing the tamper case 59 of a dense material such as lead or composite molding material such as a mixture of granulated lead or lead oxide and a thermosetting resin. Phenyol aldehyde or epoxy resins are examples of suitable resins which may be combined in a proportion of to solids to 5 to 10% resin.

The inner liner 57 in the forward section 61 serves to provide a continually reducing chamber 69 during the course of detonation. This liner serves to transmit pressure generated by the detonating high explosive to the atmosphere within the chamber 69. Preferably the liner 57 is formed of a ductile metal or may be made of plastic such as nylon, thermoplastic or thermosetting resins or rubbers. Metals such as steel, stainless steel, nickel alloys and the like have been determined to provide efficient energy transfer and minimize mixing of the liner itself with the compressed gases within the chamber 69.

When particularly light projectiles (or gases) are to be employed, the liner may effectively be of a lighter material. The light weight liner is capable of collapsing at a faster initial rate to accommodate the faster moving light projectile or gas.

The explosive charge, that is the high explosive 55, may be TNT [trinitrotoluene], PETN [pentaerythritol tetranitrate], composition B [60%cyclonite, 40%TNT and 1% wax]; composition C4 [91% cyclonite, 2.1% polyisobutylene, 1.6% motor oil and 5.3% di(2-ethylhexyl) sebacate; or any other similar high energy explosive material. Liquid high explosives may also be employed. A highly preferred liquid explosive which possesses an energy constant equivalent to that of the best solid high explosives is identified by the term NTN which is 51.7% nitromethane, 33.2% tetranitromethane and 15.1% l-nitropropane. When utilizing such a liquid explosive, considerable fabrication costs are minimized since no forming is necessary and the explosive is merely introduced into the volume between the tamper case 59 and the liner 57. Molding, machining or casting techniques can be utilized to fabricate a solid explosive with complex shape being conveniently fabricated into portions joined in the plane of the greatest diameter of the cavity 69. A thin layer 72 of a permissible adhesive such as Eastman 910 (available Eastern Chemical Products, Inc., subsidiary of Eastman Kodak Company, 260 Madison Avenue, New York, New York) or Furane (obtainable from Braun-Knecht-Heimann Company, Division of Van Waters and Rogers, Inc., San Francisco, California), may be employed to bond the component portions.

The barrel 17, attached to the explosive assembly, serves as the projectile launching means. A projectile such as a spherical ball 73 is disposed within the breach end of the tube 1'7 to complete the basic form of the projectile launching unit 16.

When supplementary or pre-excitation of the gas is to be employed, electrical conductor means such as cables 75 and 77 may be connected to the liner 57 and to barrel 17, respectively. The lines 75 and 77 are then connected to the power source 53 (FIGURE 1). With such an arrangement an intense electrical discharge may be caused between the breach end of the tube 17 and the liner 57 through a propellant gas disposed in the cavity 69. For this purpose a suitable power source 53 should be capable of providing a high discharge current in the order of 100 to 1,000 kiloamperes for a short time period in the order of a few microseconds. Power sources of this type have been used for some time in a variety of applications as in controlled thermonuclear research, radar, pulsed X-ray sources, and the like. Therefore, the design of such power source is easily within the skill of the art. A typical source may include a high voltage capacitor bank, a D.-C. charging current supply coupled intermittently to the capacitor bank for charging purposes, and a high current switch adapted to be triggered by an electrical impulse from a pulse generator 51.

In a typical operation utilizing only the propulsive force generated by the explosive charge, a selected gas is introduced into the cavity 69 either during assembly or by means of the tube 33 and by using evacuation means to remove the original gas. Optionally the barrel 17 may be evacuated if the gas is introduced during assembly. The choice of gas is determined by the consideration of several factors. Since hydrogen and other like gases such as deuterium and helium have low atomic and molecular weights, these materials, and hydrogen particularly, should provide the highest jet velocities. Corollary gases of different molecular weights should exhibit different propulsive properties thereby allowing a modification and control of the velocities generated to suit different purposes. In many instances, as in simulating interstellar space conditions, the vessel 11 (FIGURE 1) may be evacuated. In other instances, as in simulating re-entry conditions for atmospheric travel conditions, partial atmosphere or atmospheric pressure of air or other selected gas may be employed in the vessel 11. With the system, arranged as described, the detonating pulse generator 49 may be actuated by a timing sequence pulse generator 51 whereupon an explosive detonation is initiated and spreads progressively through the high explosive 55. The characteristics of the progression are determined and phased by choice of physical dimensions and certain geometrical factors to be defined hereinafter. Since the tamper case 59 does not allow significant outward motion in early stages of detonation, the explosive energy is primarily directed inwardly, exerting a very powerful compressive force upon the liner 57 causing a progressive collapse thereof as shown in FIGURE 3 of the drawing. As'a result, the propellant gas disposed in the cavity 69 is expelled at an exceedingly high pressure, velocity and temperature through the barrel 17 thereby impelling the projectile 73 at the hyper-velocities of the character described above. With the electrically excited method of operation, the sequence timer 51 may be arranged to excite propellant gas in the cavity 69 just before or simultaneously with the arrival of the detonation wave at liner 57 whereby an additive efiect to augment the propulsion forces is obtained.

The system of the invention may be utilized with a wide variety of projectiles under highly varied operating conditions for various utilitarian purposes. However, simplified computations in accordance with the classical physical theory sufiice to provide an indication of the results which may be typically obtained in accelerating a projectile body to very high velocities. Particles in the order of 0.1 gram in mass which may represent the size and mass order of magnitude characteristic of micrometeorites Will be considered.

In accordance with the classical forms of Newtons Laws of Motion, the motion of the projectile which is to be a simple spherical pellet, as shown in FIGURES 1 and 2, can be described by the following equations:

P=ma

tion.

v =2al (2) where v equals the velocity of the projectile, a equals acceleration, and 1 equals the length of the barrel 17 or other distance over which the accelerating pressure is applied.

Therefore,

x/2Pl v With ordinary cylindrical or conical explosive charges, the peak value of P may easily reach several megabars in late stages of detonation and compression. The preferred system described above is capable of generating even higher pressures. For purposes of projectile acceleration, however, the desired result is to obtain a pressure time profile within the stress limits of the projectile materials. The desired pressure pulse should effect a time average value which would exist for approximately 30 microseconds. The pressure which would be effective herein would be a time average value F for which a conservative value may be in the order of 1 equals megabar in a cylindrical system. Then with the length of the barrel equaling 30 centimeters and the mass equaling 1 g./cm. the projectile would achieve a velocity of about 2 centimeters per microsecond. Since a higher average pressure F may be obtained using the preferred system as provided herein, even higher pellet velocities may be achieved. For optimum results, the volume change produced by pellet motion over barrel length I should be approximately equal to or less than the volume of the high pressure gas at any time during the propulsion. In other terms, the volume, that is the length of the bore of the barrel 17, is proportional with the relation of the gas cavity such that the motion of the pellet does not excessively reduce the temperature of the propellant during the acceleration. Therefore, maximum energy is transferred from the compressed and heated propelling gases to the projectile. With the projectile traveling away from the gas, the original gas pressure of several megabars is reduced to the above mentioned effective pressure of approximately megabar. The shape and dimensions of the high explosives 55, the internal liner 57, the tamper case 59 may be varied considerably. A conical shape for each of these elements is relatively simple for calculation and has, consequently, been used as an example herein. Of primary importance, however, is the shape of the final contour as can be seen in FIGURE 3. FIG- URE 3 shows the liner 57 during various stages of detonation whereby its internal dimensions become continually reduced, leaving however, the orifice 71 open for the escape of propelling gases. Using a conical explosive assembly shown in FIGURE 3, the contour of the liner during various stages of detonation can be calculated as follows.

First an assumption is made that each incremental axial length of the conical liner 57 will act to first order as would infinite cylinders having the same radii. One dimentional explosion of infinite cylindrical systems can then be calculated having various initial radii. This calculation can be done on a .computer using conventional numerical methods. Also a one dimensional hydrodynamic code for this purpose has been prepared. (See, for instance, KO Hydrodynamic Code by Mark L. Wilkins, available at Physics International, Inc., Berkeley, California or Stanford Research Institute, Poulter Laboratories, of Menlo Park, California.)

FIGURE 4 shows a typical family of curves developed from such calculations. This figure shows the variation of a liner radius (for various initial radii) during implosion as a function of time. For the family of curves shown in FIGURE 4, the high explosive 55, the liner 57 and the inertial backing for tamper case 59 each have constant thickness throughout the forward area 61 (as shown in FIGURE 2). Thus each of the curves of FIG- URE 4 has a similar characteristic shape.

For any angle of the cone 61, if the detonation velocity of the high explosive is known, the successive contour of the liner can be constructed as shown in FIGURE 3. Thus, in FIGURE 3, R may be considered the initial radius of the inner liner at the point 91. R may be considered the initial radius of the liner at the point 93. D may be considered the detonation velocity of the high explosive 55 and L may be considered the distance along the liner from the point 91 to the point 93. may be considered the half angle of the cone. Then let t be the time at which the liner, at point 9]., begins to accelerate, and let t be the time at which the liner, at point 93, begins to accelerate. The difference in time of initial accelerations then may be found as:

With Equation 4, the time by which the radius time history of position 93 must be shifted with respect to the radius time history for position 91 can be calculated. For the specific curves shown in FIGURE 4, 6 will be assumed to be 22 and the detonation velocity at 0.684 centimeter per microsecond. The radius of the cone at the point 91 may be considered 16 centimeters while the radius of the cone at point 93 may be considered 12 centimeters- The time difference then becomes;

1s 12 At 15.6 microseconds In FIGURE 5, the curves of FIGURE 4 have been reproduced but with the displacement of appropriate amounts as calculated from Equation 4 for the 22 cone. To find a contour in any given time we have only to read off the appropriate radii from this curve at the desired time. The various contoured lines C C C C C and C are derived from FIGURE 5 for the various times of 16, 32, 40, 48, 52 and 56 microseconds, respectively. Thus, the actual phase velocity of the effective cone angle at the point of collapse of the liner is determined.

If the characteristics of the contour are not suitable or if it is desired to further adjust them, several means are available. The angle of the cone maybe changed, the thickness of the liner, the high explosive or the inertial backing may be changed gradually as a function of the distance along the axis of the cone. By changing the angle of the cone, a different family of curves (of the type shown in FIGURE 4) may be derived from the above mentioned hydrodynamic code of Wilkins or by other conventional means. If the thickness of the liner, the high explosive or the inertial backing tamper case is changed, a new family of curves of the character shown in FIGURE 4 will likewise be determined from the above mentioned hydrodynamic code or other methods. Alternatively, the pure conical shape may be changed to one having a slight curve as shown in FIGURE 7 wherein elements comparable to those in FIGURE 2 are designated by like reference numerals with a sufiix a. In this instance the individual curves of the family (comparable to that of FIGURE 4) would vary considerably due to the different thicknesses of high explosive and tamper case. The same principles, however, would be employed to provide the contour curves similar to those as shown in FIGURE 5. Each of the above mentioned methods are amenable to the same calculation techniques as demonstrated herein. In addition, there are two dimensional hydrodynamic codes available which can calculate any geometry having rotational symmetry.

A typical propulsive unit may have the following dimensions and characteristics made with reference to the forward section 61 of FIGURE 2:

(The dimensions and configuration of the rearward section 63 are not critical since it merely serves as an extension of the detonator 65. However, the liner 57 of this portion is notably thicker than that of its forward section whereby the implosion effect is somewhat minimized.)

Liner.Stainless steel having a thickness of approximately of an inch. Largest cavity diameter16 centimeters cavity orifice diameter-approximately l centimeter, Frustron-conical taper from the axis 22.

High explosive 55.Liquid explosive NTN (approximately 2.7 centimeters thick).

Tamper Case 59.Lead having a thickness of about 2.2 centimeters.

Gas propellant in the cavity 69.Efi"1cient energy transfer occurs when the mass of the gas such as hydrogen is about five times the mass of the projectile which yields a transfer such that a gas energy transfer of about 20% is yielded.

Barrel 17.May be about 48 centimeters. An electrical pre-excitation energy in the amount of 30 kilo- Joules may be applied.

Using a projectile of about 0.1 gram (aluminum, etc.) particle velocities in excess of two centimeters per microsecond are realized. Due to the fact that heat transfer is not rapid, little or no material is lost in the pellet in such a short acceleration length. Some gas may leak past the projectile. However, since this gas would be cooled by close contact with the projectile in the barrel wall, an advantage may result such as lower heat transfer rates, lower ablation rates, and more nearly constant pusher gas temperature.

Kinetic temperature of the gas in the order of 5 to 10 electron volts have been realized, consequently the high energy content of the gas achieved at the end of compression can be appreciated. If the projectile and barrel is omit-ted, except for a short 1 .to 2 centimeter breach section, and a thin diaphragm substituted, the heated and compressed gases can be discharged as an ultrahigh velocity jet usable for various purposes.

The heated gas appears to be the most intense light source ever contemplated other than nuclear blasts, due to the radiation rate per unit area exceeding by a factor of at least the intensity emitted by the sum per unit area. Since the particle velocity-is a Maxwellian, photons of the order of 30 electron volts will be emitted copiously. It is estimated that the energy is emitted at about 1 kilo- Joule per square centimeter per microsecond. The source is of such intensity that the radiation effects of even such extreme conditions as exist in the vicinity of a nuclear explosion can be simulated. The ejected gas jets can be used to study ablation and other effects and extend the studies performed heretofore with lower velocity jet producing means, plasmas, etc.

The circumstance that the ejected gas is substantially uncontaminated with the liner or other extraneous material is an advantage of considerable importance in such studies. In convergent systems, instability is expected such that mixing should occur between the gas within the cavity 69 and the liner 57. But, in this system, for the degree of convergence utilized this instability does not occur. For reasons which are not completely understood, the liner materials do not intermix with the ejected gases, that is, the ejection of liner and other materials are restrained by the shape of the final gas cavities and the high gas pressure, whereby usable jets of preselected composition are produced.

Modification of the projectile launching unit or explosive assembly 13 may be made as shown in FIGURE 6. In some instances, where it is desired to minimize the projection of fragments of the projectile launching unit lengthwise through the vessel 11, the orientation of the barrel 17b with respect to the explosion assembly 13 may be altered. For this purpose, the explosive assembly 13 may be mounted with the axis thereof being at an inclined angle with respect to the axis of the barrel 17b. In addition, a modified launch tube 101 may be employed as shown in FIGURE 3. The breach portion 103 includes a short length of barrel similar to that of the barrel 17. However, the outer length 105 of the barrel is made with the bore slightly larger in diameter than the diameter of the projectile. Accordingly, when the projectile 107 traverses the bore length 105, propellant gases blow by uniformly on all sides and the projectile is substantially suspended by the laminar flow and is centered and guided by aerodynamic forces.

The projectile may be composed of any material suitable of being formed as desired for the particular experiment ,or other useful purpose and, likewise, it may take a wide variety of forms, although round and ellipsoidal projectiles should be useful for most purposes. Moreover, selected fore and aft or other exterior surfaces may be coated with an ablative material to minimize loss of pellet material or to study the ablated properties of the materials and/ or various projectile shapes. Lightly compacted particulate material, cemented spherical ball aggregations and the like, may be employed as projectiles to simulate dust clouds, micrometeorite storms, etc. Explosive charges may be disposed in the projectile to explode on contact with the target. Elongated cylindrical projectiles having a flat or curved end surface may likewise be employed. Even relatively long thin rods having a high sectional density may be employed. Low density projectiles may be prepared having a porous core and with thin foil covering. Other means may be employed for disposing the propelling gas in said cavity. For example, pre-exciting electrical discharge can be arranged to vaporize and ionize hydrogen from a material such as titanium hydride or lithium hydride.

l0 While there has been described in the foregoing what may be considered preferred embodiments of the invention, modifications may be made therein and it is intended that all such modifications be within the scope of the invention.

We claim:

1. A projectile launching apparatus assembly including in combination a conical body of a high explosive material having provided therein a cavity formed symmetrically about the axis, said cavity terminating in a neck portion on one end surface of said conical body, a compressible liner disposed in said cavity, gaseous material disposed within said compressible liner, a tamper case enclosing said high explosive body and having an orifice corresponding to the neck portion of said cavity, detonator means including at least one high explosive detonator associated with the second end of said explosive body and arranged to provide a detonation pattern in said high explosive efiective .to compress said liner and gaseous material in a continuous manner progressive toward said neck portion, said material thereby being ejected from the neck portion of said cavity as a very high velocity collimated jet, launch tube means having the breach oriented to receive said high velocity collimated jet axially therethrough, and a projectile body disposed in the breach of said tube.

2. Apparatus as defined in claim 1 wherein said launch tube is arranged with the axis thereof at an inclination to the axis of said jet.

3. Apparatus as defined in claim 1 wherein said high explosive material is a solid body of high explosive.

4. Apparatus as defined in claim 1 wherein said high explosive is a liquid high explosive.

5. Apparatus as defined in claim 1 wherein the high explosive body is provided with a cavity, having a wall portion terminating in said neck portion with a frustoconical configuration.

6. Apparatus as defined in claim 1 wherein said launch tube and said liner are provided with an electrical discharge gap therebetween and electrical conductor means are provided for coupling an electrical discharge power source therebetween.

7. A hyper velocity system comprising an elongated cylindrical housing defining a chamber, gas evacuation and supply means coupled to said chamber to provide a controlled atmosphere environment in said chamber, and a hyper-velocity projectile launching unit disposed in said chamber, said hyper-velocity launching assembly comprising a conical body of a high explosive material having provided therein a reentrant cavity formed symmetrically about the axis, said cavity terminating in a neck portion on one end surface of said conical body, a compressible liner disposed in said cavity, a tamper case enclosing said high explosive body and having an orifice corresponding to the neck portion of said cavity, detonator means including a high explosive detonator having at least one detonator associated with the second end of said explosive body and arranged to provide a detonation pattern in said high explosive effective to compress said liner and gaseous material in a continuous manner progressively toward said neck portion, said material thereby being ejected from the neck portion of said cavity as a very high velocity collimated jet, launch tube means having the breach oriented to receive said high velocity collimated jet axially therethrough, and a projectile body disposed in the breach of said tube.

8. A hyper-velocity system as defined in claim 7, together with electrical conductor means coupled to provide an electrical discharge between said launch tube and said liner in said cavity.

9. Apparatus as defined in claim 8 together with a power supply coupled to said electrical discharge means, and wherein there is included sequence timer means arranged to fire said detonator and actuate said power supply to produce said electrical discharge.

10. A high explosive assembly for producing a very high velocity, high temperature propellant gas jet, said assembly comprising:

(a) a body of high explosive having an elongated cavity formed symmetrically about the axis of the body, said cavity having an opening disposed at one end thereof;

(b) a compressible liner covering the surface of said high explosive which constitutes the wall of said cavity therein;

() a tamper case confining the exterior surface of said high explosive;

(d) means for introducing a gaseous propellant material into the space in said cavity defined by said liner and means for confining said gaseous material within said space; and

(e) detonator means disposed along said axis adjacent the end of said cavity opposite the end thereof in which said opening is disposed, said cavity being shaped and said detonator means being arranged relative thereto to provide a detonation pattern in said high explosive effective to compress said liner and said confined gaseous material in a continuous manner progressively toward said opening, whereby to eject said gaseous material through said opening in the form of said high velocity jet.

11. A projectile launching apparatus assembly, comprising:

(a) a body of high explosive formed with an elongated cavity therein about the axis of the body, said cavity terminating in a neck portion at one end thereof;

(b) a compressible liner covering the surface of said high explosive which constitutes the wall of said cavity therein;

(c) a projectile disposed adjacent said neck portion;

(d) a tamper case confining the exterior surface of said high explosive;

(e) means for introducing a gaseous propellant material into the space in said cavity defined by said liner; and

(f) detonator means disposed adjacent the end of said cavity opposite the first-named end thereof, said cavity being shaped and said detonator means including at least one detonator disposed along said axis and arranged relative to said cavity to provide a detonation pattern in said high explosive eifective to compress said liner and said gaseous material in a continuous manner progressively toward said neck portion to cause said compressed gaseous material to be ejected through said neck portion, and thereby launch said projectile, said ejection of said gaseous material causing the gaseous material to follow and continuously push said projectile forwardly.

12. A projectile launching apparatus assembly including in combination:

(a) a body of high explosive having a relatively elongated cavity formed symmetrically about the axis of the body, said cavity terminating in a neck portion at one end thereof;

(b) a tamper case confining the exterior surface of said high explosive;

(c) a compressible liner covering the surface of said high explosive which constitutes the wall of said cavity therein;

(d) means for introducing a gaseous propellant material into the space in said cavity defined by said liner, and means for confining said gaseous material within said space;

(e) detonator means disposed adjacent the end of said cavity opposite the first-named end thereof, said detonator means including at least one detonator disposed along said axis and arranged relative to said cavity to drive said liner in a continuous manner progressively toward said neck portion to compress said gaseous material and eject the same through said neck portion as a high temperature, high velocity collimated jet; and

(f) a launch tube having the breech end thereof disposed to receive said collimated jet as the latter is ejected from said neck portion.

13. A projectile launching apparatus assembly as defined in claim 12 wherein said launch tube means is axially aligned with said jet.

14. A projectile launching apparatus assembly as defined in claim 12 wherein the axis of said launch tube is inclined to the axis of said jet.

15. A projectile launching apparatus assembly as defined in claim 12 and having projectile means disposed in said launch tube.

16. A projectile launching apparatus assembly as defined in claim 12 wherein said launch tube has a uniform bore diameter.

17. A projectile launching apparatus assembly as defined in claim 12, wherein said launch tube has a bore diameter at the breach end thereof equivalent to the diameter of said projectile mean and having a larger bore diameter along the length thereof between its breech end thereof and its muzzle end.

18. An apparatus assembly as defined in claim 15 wherein said high explosive body is generally conical and said neck portion of said cavity terminates in an end surface of said body.

References Cited by the Examiner UNITED STATES PATENTS 429,594 6/90 Bartlett 898 2,185,523 1/40 Routledge 42-76v 2,783,684 3/57 Yoler 897 2,790,354 4/57 Yoler et a1. 898 2,872,846 2/59. Crozier 897 2,882,796 4/59 Clark et al. 897 2,892,407 6/59 MacLeod 102 3,054,329 9/62 Willig 89-8 3,065,695 1 1/6 2 Jarrett 102 3,109,305 11/63 Kilmer et al. 897 X BENJAMIN A. BORCH'ELT, Primary Examiner.

SAMUEL FEIN BERG, SAMUEL W. ENGLE,

Examiners. 

1. A PROJECTILE LAUNCHING APPARATUS ASSEMBLY INCLUDING IN COMBINATION A CONICAL BODY OF A HIGH EXPLOSIVE MATERIAL HAVING PROVIDED THEREIN A CAVITY FORMED SYMMETRICALLY ABOUT THE AXIS, SAID CAVITY TERMINATING IN A NECK PORTION ON ONE END SURFACE OF SAID CONICAL BODY, A COMPRESSIBLE LINER DISPOSED IN SAID CAVITY, GASEOUS MATERIAL DISPOSED WITHIN SAID COMPRESSIBLE LINER, A TAMPER CASE ENCLOSING SAID HIGH EXPLOSIVE BODY AND HAVING AN ORIFICE CORRESPONDING TO THE NECK PORTION OF SAID CAVITY, DETONATOR MEANS INCLUDING A T LEAST ONE HIGH EXPLOSIVE DETONATOR ASSOCIATED WITH THE SECOND END OF SAID EXPLOSIVE BODY AND ARRANGED TO PROVIDE A DETONATION PATTERN IN SAID HIGH EXPLOSIVE EFFECTIVE TO COMPRES SAID LINER AND GASEOUS MATERIAL IN A CONTINUOUS MANNER PROGRESSIVE TOWARD SAID NECK PORTION, SAID MATERIAL THEREBY BEING EJECTED FROM THE NECK PORTION OF SAID CAVITY AS A VERY HIGH VELOCITY COLLIMATED JET, LAUNCH TUBE MEANS HAVING THE BREACH ORIENTED TO RECIEVE SAID HIGH VELOCITY COLLIMATED JET AXIALLY THERETHROUGH, AND A PROJECTILE BODY DISPOSED IN THE BREACH OF SAID TUBE. 